The manufacture of multi-paned window lights for use in the glazing of windows and doors requires that a controlled insulative distance be kept between the adjacent glazing panel panes. Ideally, this gap distance should be defined by a peripheral frame, which is hermetically sealed to the spaced apart panes thus creating a confined "dead air" space, which may optionally be filled with an improved insulative gas.
Such spacer frames have usually been roll-formed, using tubular type aluminum profile sectioned frame materials, the hollow interior of which frequently serves to contain moisture vapor desiccants, for the removal of any moisture that may be present within the sealed construction. While such metal spacers form an effective moisture vapor barrier, they also possess high thermal conductivity characteristics, with a conductivity coefficient "k" value in excess of 117 which can create a thermal bridge between the panes being separated unless thermally isolated or "broken". Such thermal bridges can lead to the accumulation of moisture, as condensation and frost on surfaces of the glazing panel adjacent the seals, at the panel periphery. Such accumulations are undesirable aesthetically as well as being potentially destructive to adjoining structures, due to staining and moisture damage.
While the provision of an intermediate thermal break can enhance the insulative performance of such metallic seal, such constructions are expensive, costing as much per lineal foot as ninety cents (Canadian).
Thermally insulative spacers have been made from thermosetting and thermoplastic materials by the pulltrusion or by extrusion process, which spacers have overcome the thermal insulative problem, but have failed to durably respond to the sealing requirements of low gas permeability and resistance to sunlight degradation due to the action of ultra-violet light energy, and their use has led to internal "fogging" of the glazing panel due to outgassing of hydrocarbon vapours from the plastics used, which vapours can condense on the internal faces of the inner and/or outer panes. The developing use of special glazing glasses has tended to exacerbate ultra-violet degradation by tending to reflect and build up the ultra-violet level.
The use of oriented sheet plastics material in forming a seal section, in order to achieve high impermeability against gas or moisture penetration, encounters problems when thermal conditions are such that the material annealing temperature is reached. At such temperatures mechanical stresses as high as, and often over 14000 pounds per square inch may be released as the spacer material returns to its pre-oriented condition.
Other known spacers include those having a stabilizing aluminum core and a body of mastic type compound. The core is susceptible to thermal bridging.
Sponge like cellular silicones present problems of permeability, structural integrity and require mechanical support.
It will be further understood that, in addition to thermal insulation and gas encapsulation and retention performance, which are particularly important, the requirement also exists for practical, low cost, effective spacers that require a minimum of waste during fabrication, lend themselves to ready formation and installation, and which provide for the incorporation of absorbents for moisture vapor and other hydrocarbon gases, to extend the service life span of a sealed, insulative glazing panel.
Various aspects of the prior art are to be found in the following United States patents which are directed to multi-paned window systems and components thereof.
______________________________________ 49,167 August 1865 Stetson 3,314,204 April 1967 Zopnek 3,280,523 October 1966 Stroud et al. 4,015,394 April 1977 Kessler 4,109,431 August 1978 Mazzoni et al. 4,658,553 April 1987 Shingawa 4,719,728 January 1988 Erikson et al. 4,649,685 March 1987 Wolf et al. 4,567,841 March 1986 Lingemann 4,564,540 January 1986 Davies et al. 4.226,063 October 1980 Chenel 4,222,213 September 1980 Kessler 4,113,905 September 1978 Kessler 4,198,254 April 1980 Laroche et al. 3,965,638 June 1976 Newman 3,935,683 February 1976 Derner et al. ______________________________________
In various solutions, ranging from Stetson to Derner et al., various aspects of spacer provisions, and of their respective limitations may be fairly readily identified by those skilled in the art.
In addition to avoiding undesireable complexity, the costing aspects of each spacer system must be born in mind as well as the need to achieve a reliable sealing life expectancy for the spacer. An established, long term life of several years duration is required to prove seal effectiveness. Anything less is commercially unacceptable.
A further, highly significant aspect of any spacer system is its suitability for assembling into window units. Factors such as ease of handling; handling robustness; longitudinal and lateral stiffness; ease of cutting to length and facility for forming joints, particularly corner joints; seal component compatability for receiving adhesives on selected surfaces, are all relevant factors in determining the suitability of a seal/spacer system.
Thus, for example, in the case of pultruded, glass reinforced plastic sections, these are generally of considerable thickness, which complicates corner formation, upon making-up a seal "frame". They are also a comparatively high cost item.
Thus, to sum up the various aspects of a seal system, it should be born in mind that an ideal spacer system should be of low cost; should possess extremely high resistance to gas percolation therethrough; be suitably constituted to traverse the corners of the panes; possess high resistance to degradation; be laterally flexible, readily applied, and effectively adhered and edge- sealed; structurally stable; of sufficient mechanical strength for installation; and possessing a low edge-to-edge thermal conductivity factor.